Propeller blade



PROPELLER BLADE Original Filed June 26, 1935 I I INVENTOR 11 2 J52, squares @4 y A ORNEYS. Y

1 blade.

Patented M... 21,1939

. PROPELLER. BLADE John Squires, Detroit, Mich assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Original application June 26,- 1935, Serial No; 28,393. Divided and this'application June 15,

1938, Serial No. 213,865

9 Claims.

This invention relates to an improved propeller blade and is a division of my copending application Serial No. 28,393, flied June 26, 1935.

More particularly the invention pertains to improved hollow propeller blades.

One of the main objects of the invention is the provision of a propeller blade which has certain of its edge portions formed to relatively fine being free from excessive creasing and other weakening characteristics;

Another object of the invention is the provision of preformed leading and trailing edge por- 5 tions in a hollow propeller blade which are, free from strains and stresses normally resulting from twisting of such portions of a propeller blade into a desired spiral contour during formation thereof. A still further object of the invention is to provide an improved tubular propeller blade which has substantially flawless leading and trailing edges that conform to propeller airfoil contour requirements, the trailing edge portion having a relatively fine taper. Y Other objects of the invention are to provide a propeller blade of this kind which has preformed leading and/or trailing edge providing portions; and to provide preformed internal grooves at the leading and trailing edge portionsof a hollow 80 metal propeller blade which reduce the weight of the latter without impairing its strength and by virtue of which the leading and trailing edge portions of the blade are free of excessive stresses.

A further object of the invention is to provide integral metal fin sections at the leading and/or trailing edge portions of a hollow propeller blade which are free from welded or pressed together component layers or thickness of the wall structure of the blade.

Additional objects of the invention are to provide a hollow propeller blade which has leading and trailing edge portions comprising integral solid metal and whichare self-sustaining in longitudinally spiraled contour independently of the side wall portions of the blade, andto provide integral solid metal leading and trailing edge portions having a greater thickness than the adjoining parts of the side wall portions thereof and which are free from compressed or welded.

together layers of the side wall portions of the The above being among'the objects of the present invention, the same consists of certain novel features of construction of propeller blades, as

a above pointed out, as will be more specifically tapered cross-section and yet devoid of cracks in its internaland external wall surfaces as well as brought out in connection with the following description, reference being had to the accompanying drawing forming a part thereof.

Illustrative embodiments of the invention are shown in the accompanying drawing, in which: Fig. l is a side elevational view of a piece of tubular stock suitable for the formation of propeller blade blanks and propeller blades embodying the invention;

Fig. 2 is a transverse sectional view taken on the line 2-2 of Fig. 1; I f

Fig. '3 is a side elevational view of an arbor which may be employed in manufacturing propeller blades embodying the invention;

Fig. 4 is a fragmentary side elevational view,

partly in section, of rolling apparatus for, and

illustrating the formation of the stock shown in Fig. 1, to the tapered tubular contour of the arbor shown in Fig. 3;

Fig. 5 is a transverse sectional view of an arbor having a spbstantially completely rolled blank thereon;

Fig. 6 is a side elevational view of a partially formed blank showing the latter as itappears after being removed from the arbor and subjected to an outer end closing operation;

Fig. '7 is a transverse sectional view taken on the line 1'I of Fig. 6;

Fig. 8'is a transverse sectional view taken on the line 8-8 of Fig. 6; v

Fig. 9 is a transverse sectional view taken on the line 99 of Fig. 6;

Fig. 10 .is a side elevational view of a finished propeller blade embodying the invention;

Fig. 11 is a transverse sectional view taken the line H-H of Fig. 10;

Fig. 12 is a.transverse sectional view taken on the line l2l2 of Fig. 10; and,

Fig. 13 is an enlarged sectional view of a blade I formed in accordance with the invention showing the edge portions thereof somewhat in detail.

In the drawing is illustrated the formation of a propeller blade embodying the invention which has a flange on its root end portion. Propeller blades embodying the invention may, however, be provided with reduced or straight root end portions. An improved propeller blade may be produced from a piece of stock, generally designated in Fig. 1 by the numeral 40, of cylindrical shape and provided with a radial flange 42 on its extremity which may be internally supported upon anarbor 43. ,The arbor 43 has a tapered contour corresponding with the interior contour desired in the finished blank from which the propeller blade is to be formed. Where the finished propeller blade is to have one or more preformed edges, the arbor will be provided accordingly with one or more groove forming ribs. In'the present case it is presumed that two preformed edges are to be provided, one at the leading edge and one at the trailing edge and in'such case there is provided on the arbor 43 integral outwardly ex:- tending ribs 44 and 45 which extend mainly ion- 5 gitudinally of the arbor. The ribs 44 and 45 have for their function formation of grooves of predetermined cross-sectional shape in those portions of a tubular, or hollow shell-like blank from which the trailing and leading edge portions of a finished propeller blade are formed. The end portions of the ribs 44 and 45, at the small end of the arbor, are disposed in diametrically opposite relationship in a horizontal plane. In a propeller blade designed for rotation in one direction, successively leftward portions of the ribs 44 wind upwardly from the central horizontal plane of the arbor and successively leftward portions of the rib 45 wind downwardly from this plane, as shown in Fig. 3, whereas in a propeller blade designed for rotation in a reverse direction the wind of the finswould, accordingly, be in an opposite direction. This formation of the ribs gives them a somewhat spiral course which is predetermined so that the grooves formed thereby in a tubular blank will correspond to the twist of the leadin and trailing edge portions of a finished blade re- ..spectively. In some instances, the substantially straight fins may be employed in which case they are brought to the'desired leading and trailing edge contour of a finished propeller blade in a forming operation of the type hereinafter described.

The cross-sectional shape of the ribs 44 and 45 at successive transverse sections of the arbor also correspond with the cross-sectional shape desired of the grooves formed thereby at corresponding transverse sections of the tubular blank. These ribs preferably have arcuately curved sides which form sides of corresponding curvature on the internal grooves of the finished blank so as to prevent the excessive creasing of the metal at the leading and trailing edge portions of the blank during bending thereof to final blade shape.

The first step of the blank forming operation comprises tapering the tubular stock while intemally supported upon the arbor 43 between suitably formed rolls, generally designated in Fig. 4

v by the numerals 46 and 41, respectively, and which are illustrated in detail in my co-pending application Serial No. 28,393, of which this application is a division. These rolls are mounted upon respective shafts having axes substantially in the same vertical plane and they are driven in the respectively. opposite direction by suitable driving apparatus (not shown). The peripheries of the rolls 45 and 41 are provided with registering, complementary arcuate grooves 54 and \i, which vary in depth and in radius of curvature at successive radial sectionsoftheroll froma maximum depth and radius of curvature corresponding to the duter'diameter of the finished tubular blank at the root end portion thereof, to a minimum depth and radius of curvature corresponding to the outor diameter of the finished tubular blank at the outer smaller end portion thereof.

70 The eccentricity of successively adjacent portions oftheperipheriesoftherollsmay.ifdesired,besopredeterminedastotaperthewall thlckness-oftbetuhilarblankfromamaximum end portionto aminimum outer entremitydurlngthe roll-- ing operations or to bringthe thickness of the wall to different predetermined values at selected sections of the blank. I

The concaved peripheries 50 and 5| of the rolls 45 and 4! have circumferences equal in length to the distance from the outer side face of the flange 42 to the outer end of the blank. Formed in the inner portion of the wall of the concaved peripheries 50 and 5| are grooves 52 and 53 which correspond roughly in cross-section to the cross-section of the ribs 44 and 45, respectively, of the arbor 43. These grooves vary in shape at diverse sections of the rolls in accordance with the shape of corresponding sections of the fins of the blank which they are relied upon to form, as well as with respect to the related sections of the edge portions of the propeller blade which is made therefrom. The grooves 52 and 53 of the rolls 45 and 4'! extend diagonally in opposite directions with respect to the widths of the concaved peripheries 50 and 5| of the rolls, respectively, and they are so formed as to register with the ribs 44 and 45 of the arbor 43 during the passage of the arbor between rolls. The cross-sectional areas of longitudinally spaced sections of the ribs 44 and 45 are smaller than the corresponding cross-sectional areas of the grooves 52 and 53, respectively. This difference in area provides space between the walls of the grooves and sides of the ribs into which metal of the wall structure of the stock 40 is flowed under the compressive and elongating forces to which the stock -40.is subjected in passing between the rolls preferably while heated to deformable state. In some instances, particularly in the formation of relatively small blanks, the metal stock may be cold worked between the rolls.

Co-axially mounted with the'rolls 46 and 41 is a pair of finishing rolls 54 and 55 having complementary concave peripheries 55 and 51 which also vary circumferentially of the rolls from a maximum depth and radius of curvature corresponding to the radius of curvature of the root end'portion of the finished blank, to a minimum depth and radius of curvature corresponding to the radius of curvature of the outer small end portion of thefinished blank. The marginal portions 58 and 59 of the rolls 54 and 55 are eccentric with respect to the axis of the rolls and they are so constructed and arranged as to operate upon the fins of the blank in order to bring them to a predetermined shape and tapering fineness during passage of the blank between the rolls. The sectioned portions at the right of Fig. 4 illustrate the manner in which the marginal portions 58 and 59 operate upon the fins at the rootend portion of the blank. These marginal portions of the rolls 54 and vary in radii between the root end of the blank and the small end thereof in such a manner as to correspond with the wind of the fins between the two extremities of the blank. I

In the formation of the piece of tubular stock 40 into a tapered fin blank, the stock is heated to a desired state of plasticity and then brought to the contour of the arbor 4; preferably in the manner set forth in my application of which this is a division, by first subjecting about one-fourth of the length of the stock, while heated and supported on the arbor, to'a rolling action between the correspondingly deeper portions of the grooves 54 and II ofth'e rolls and 41, respectively. Thereafter the successive remaining portions of the stock are similarly operated upon between the rolls and 41 until the-entirelength of the -nr s igs into an integral structure.

. end poi-tion 9ll-of-the blank may then be cut to 75 line Ql shownin Fig. 6.

stock has been brought to the contour of: the exterior of the arbor. After the first'pass of the stock betweenthe rolls 46 and 41, the arbor with the stock thereon is removed from the latter rolls 5 and turned with respect to its axis throughout substantially 90 degrees and it' is then fed between the finishing rolls 54 and 55. The stock may be brought to conformity with the entire length of the arbor in any desired number of 10 passes butit is preferred to employ four passes between each of which the stock and the arbor are advanced substantially one-fourth of the originallength of the stock, it being understood that the stock is subjected to treatment between 5 the finishing rolls after each pass between the rough forming rolls. The stock alone or the stock in the arbor may be heated between successive passesbetween the successive series of rolls, if necessary, maintain a desired plasticity of the 20 metal. I

At the end of the rolling operation the blank conforms to the tapered contour of the arbor 43 as illustrated in Fig. 5, wherein the blank is generally designated by the numeral 64. The re- 25 lated grooves and ribsof the rolls 48 and 41 form the trailing edge fin,- designated by the numeral 65, and the leading edge fin designated by the numeral. The leading edge fin 66 preferably has a rounded contour and it registers with an 30 internal groove 61 formed by the rib 44 of the arbor. The trailing edge fin G5 is substantially solid and has a tapering cross-section terminating in a comparatively fine outer edge portion. The fineness of the outer edge of this fin varies at spaced longitudinal cross-sections of the blank so as to predetermine the shape of the leading andv trailing edges of the blade subsequently formed from the blank at corresponding transverse sections of the finished product. Register- 40 ing with the trailing edge fin 65 is an internal groove 68 whichis preferably of rounded crosssection. This groove and the groove 61 provides a definite line of demarkation between the edge ished product by excessive creasing of the metal at such edge portions.

I The arbor 43 is then removed from its position within the tapered blank shown in Fig. by the use of any suitable arbor pressand the small endof the blank is closed in any desired manner, for example as illustrated inmy application of which 55 this is a diVi-SiOIl.

After the arbor 43 is'removed following the rolling operation the blank is-in the form shown in section in Figs. '7 8 and 9 and has leading and trailing edge fins 66' and 65'. These fins vary in 0 cross-section at successive sections of the blank in accordance with corresponding cross-sections of the leadingand trailing edges of the finished propeller blade. The trailing fin 65' is preferably wider and of more tapering contour than the 65 leading fin in order to fulfill the requirements of airfoil contour. Whenthe arbor is removed, the small end of the blank is flattened in the plane of the adjacent end portions of the fins 65' and 65C and this flattened end portion 90 is heated in any 70 suitable manner sufiiciently to weld together the superimposed layers of metal of which it con- The flattened any desired state, as for example upon the dotted By the term tubular blank used herein and .in the claims, is meant any suitable hollow or shell like structure regardless of its cross-sectional or longitudinal sectional contour. When the tubular blank is completed it is then pressed to blade shape betweensuitable dies with the fins and the grooves of the blank disposed so as to register with the leading and trailing edge forming portions of the dies, respectively. One form of compression dies and associated apparatus is shown in my application of which this is a division, and which also illustrates the manner in which a tubular blank of the type shown in Fig. 6 is operated upon during this step of the blade forming process.

During compression of the blank between die parts to bring it to blade shape precaution is taken tobring the fins 65' and 66' into proper registration with the portions of the dies which form the trailing and leading edge portions I12 and I'll! of the finished blade I13 shown in Fig. 10.

The trailing edge "2 is preferably formed to a finely tapered cross-section having a maximum thickness, as illustrated substantially equal to the combined thicknesses of the adjacent side wall portions in Fig. 13, in order to bring the blade into accurate conformity with streamline requirements and the leading edge is preferably rounded and'thick'ened for this same pumose, the transverse cross-section thereof being alrcuately shaped and of greater thickness than 'the adjacent parts of theside wall portions. e presence of the fins and associated grooves of the blank make it possible to procure a much more finely tapered trailing edge than could otherwise be obtained without creasing the wall structure of the blade so radically that its structural strength would be impaired if this edge portion of the blank. were not in fact cracked. Tendency of the finished blade to be untwisted by the relatively solid edge portions is guarded against by forming the fins of the blank to the contour of the wind or pitch of the blade during the blank forming operation. Although probably the greatest advantage is derived from forming the trailing edge portion of a propeller blade to the above construction, considerable benefit is gained in many instances by also preforming the leading edge in the manner herein set forth for the curvature of the latter may be'predetermined without injuring the wall structure of the blade and theleading edge may be conveniently brought to a greater thickness than the remaining portions of the walls of the blade so as to-render the leading edge more rigid and resistant to deformation.

When propellerblades having different pitches as requiredfor propellers that are designed for operation at different speeds are to be formed from blanks of the same character, the fins of the blanks can be made substantially straight and then later brought to the desired leading or trailing edge contour in the blade forming operation. In rolling or otherwise forming the stock to ness thereof may be predetermined so that the finished propeller blade will have a varying wall thickness proportioned at successive sections to tapered, hollow, shell-like contour, the wall thicksustain the corresponding varying stress'to which such sections are subjected.

Although but one form of the invention has been illustrated and described in detail, it will be apparent to those skilled in the art that various modifications may be-made without departing WhatIclaimim' metal body structure, and an integral preformed substantially solid edge portion conforming in cross-section to air foil contour.

. 2. A hollow metal propeller blade including a. pressed tubular body structure and an integral preformed edge part having an inner portion of greater thickness than the adjacent wall structure of said blade and having a finely tapered outer portion.

3. A hollow metal propeller blade including a seamless pressed tubular body structure, and an integral preformed edge portion.

4. A hollow metal propeller blade comprising a pressed tubular-body structure having a varying wall thickness proportioned at successive sections to sustain the corresponding varying stress to which said sections are subjected, and an integral preformed rolled edge portion.

5. A hollow metal propeller blade including a pressed tubular body portion having opposite *side wall portions, and a leading edge portion comprising integral solid metal of tapered transverse cross-section and having a maximum thickness substantially equal to the combined thicknesses of the adjacent parts of said side wall portions.

6. A hollow metal propeller blade including a pressed metal body portion and opposite side wall portions, and a trailing edge portion comprising integral solid metal and having 'an arcuately shaped transverse cross-section of greater thickaess than the adjacent parts of said side wall porons.

1. A propeller blade including a pressed tubular 'l. A hollow metal propeller blade including a pressed tubular body structure having opposite side wall portions, and a leading edge portion, said leading edge portion comprising integral solid metal of tapered transverse cross-section and having a maximum thickness substantially equal to the combined thicknesses oi. the adjacent parts of said side wall portions, said leading edge portion being preformed and self-sustaining in iongitudinally spiral contour independently 01. said side wall portions.

8. A hollow metal propeller blade including a pressed tubular body portion having opposite side wall portions, a leading edge portion, said leading edge portion comprising integral solid metal of tapered transverse cross-section and having a maximum thickness substantially equal to the combined thicknesses of the adjacent. parts of said side wall portions, and-a trailing edge portion comprising integral solid metal and having an arcuately shaped transverse cross-section of greater thickness than'the adjacent parts of said wall portions.

9. A hollow metal propeller blade including a pressed tubular body portion having opposite side wall portions, and a leading edge portion, said leading edge portion comprising integral solid metal of tapered transverse cross-section having a finely tapered exterior longitudinal extremity and a grooved internal longitudinal extremity serving as a definite line of demarcation between the adjacent parts of said side wall portions.

' JOHN SQUIRES. 

